1. Field of the Invention
The present invention relates to an evaporator, especially to a low boiling point medium evaporator which generates a low boiling point medium vapor from the two component mixture with different boiling points, by heating.
2. Description of the Prior Art
FIG. 1 shows the evaporate of the prior art which evaporates the low boiling point medium from a two component mixture with different boiling points.
The upper header 12 and the lower header 14 are connected by risers 16 with small diameter and a down comer 18 with a large diameter. The outlets of the risers 16 are provided at the duct 20 in the upper dram 12, and cyclone separators 22 are mounted at the both sides of the duct 20. An exhaust pipe 24 and a supply pipe 26 are mounted on the upper dram 12.
In the risers 16, two component mixture 101 is heated with heating gas 104 and the low boiling point medium vapor 102 is generated and the vapor-liquid two phase flow is guided into the duct 20 of the upper dram 12. This is separated into the low boiling point medium vapor 102 and the two component mixture 101 by the cyclone separators 22. The separated low boiling point medium vapor 102 is discharged from the exhaust pipe 24. The low boiling point medium liquid 103 is mixed into the remaining two component mixture 101 from the supply pipe 26, and, after heat exchange, it is circulated through the down comer 18 to the lower dram 14.
The low boiling point medium 102 and 103 can be freon R 113, for example, and the two component mixture 101 can be the mixture of freon R 113 and polyol ester oil. The reason of adopting the two component mixture 101 of oil and freon as a heat exchange medium is that durability to thermal decomposition of the low boiling point medium is accelerated and that it can be exposed to higher temperature than the low boiling point pure medium by adding oil to the low boiling point medium. In the said conventional art, however, the heated and generated vapor is the low boiling point pure medium and has a defect of being easily decomposed by heat because it is superheated vapor of high temperature. Moreover, another defect is that the oil-rich two component mixture 101 and the low boiling point medium liquid 103 are not mixed satisfactorily at the upper dram 12.
Taking the above defects into consideration, the purpose of the present invention is to offer the low boiling point medium evaporator which prevents thermal decomposition of the low boiling point medium vapor without lowering the pressure drastically and carries out mixing the two component mixture and the low boiling point medium liquid satisfactorily.